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Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 151

Write formulas for the following compounds: (a) Lithium phosphate (b) Magnesium hydrogen sulfate (c) Manganese(II) nitrate (d) Chromium(III) sulfate

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Identify the ions involved in each compound: (a) Lithium (Li^+) and phosphate (PO4^{3-}), (b) Magnesium (Mg^{2+}) and hydrogen sulfate (HSO4^-), (c) Manganese(II) (Mn^{2+}) and nitrate (NO3^-), (d) Chromium(III) (Cr^{3+}) and sulfate (SO4^{2-}).
Determine the correct ratio of cations to anions needed to balance the overall charge to zero for each compound.
For lithium phosphate, combine three lithium ions (Li^+) with one phosphate ion (PO4^{3-}) to balance the charges, resulting in the formula Li3PO4.
For magnesium hydrogen sulfate, combine one magnesium ion (Mg^{2+}) with two hydrogen sulfate ions (HSO4^-) to balance the charges, resulting in the formula Mg(HSO4)2.
For manganese(II) nitrate, combine one manganese(II) ion (Mn^{2+}) with two nitrate ions (NO3^-) to balance the charges, resulting in the formula Mn(NO3)2. For chromium(III) sulfate, combine two chromium(III) ions (Cr^{3+}) with three sulfate ions (SO4^{2-}) to balance the charges, resulting in the formula Cr2(SO4)3.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Compounds

Ionic compounds are formed when metals transfer electrons to nonmetals, resulting in the formation of positively charged cations and negatively charged anions. The electrostatic attraction between these oppositely charged ions leads to the creation of a stable compound. Understanding the charges of the involved ions is crucial for writing correct formulas.
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Polyatomic Ions

Polyatomic ions are ions composed of two or more atoms that are covalently bonded and carry a net charge. Common examples include sulfate (SO4^2-) and phosphate (PO4^3-). Recognizing these ions and their charges is essential for accurately combining them with metal ions to form the correct chemical formulas.
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Nomenclature Rules

Chemical nomenclature rules provide a systematic way to name compounds based on their composition and structure. For ionic compounds, the name of the metal is followed by the name of the nonmetal or polyatomic ion, with appropriate prefixes or suffixes to indicate oxidation states when necessary. Familiarity with these rules is vital for translating compound names into their corresponding chemical formulas.
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